Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$196.85	13.747%	$223.911	$223.91	$223.90	$223.90
Purchase #2	$166.70	10.805%	$184.7119	$184.71	$184.70	$184.70
Purchase #3	$40.78	11.253%	$45.369	$45.37	$45.35	$45.40
Purchase #4	$29.56	10.328%	$32.613	$32.61	$32.60	$32.60
Purchase #5	$130.36	12.420%	$146.5507	$146.55	$146.55	$146.60
Purchase #6	$108.96	7.723%	$117.375	$117.38	$117.40	$117.40
Purchase #7	$29.70	10.549%	$32.8331	$32.83	$32.85	$32.80
7 purchase totals =	$702.91		$783.3637	$783.36	$783.35	$783.40